Population abundance and dispersal in Akodonazarae (pampean grassland mouse) in Argentina

Dispersal of Akodon azarae, the pampean grassland mouse, was studied during different phases of the annual cycleof population abundance in longitudinal habitats in agroecosystems. Dispersal rates were higher in the increasing and decliningphases than at times of low and peak densities. The pattern of variation in dispersal rates may have been caused by bothpopulation dynamics and structure, as well by changes in habitat variables that influence rodent survival and reproduction. Lowdispersal rates in spring were related to reproductive activity, which restricts females’ movements and causes large movementsof males within their home ranges. In autumn, with increasing density, dispersal should be a good strategy for individuals thatdid not gain access to vacant sites. In contrast, in early winter, when density is high and there are no vacant sites, the costs ofdispersal (mortality and competition) are not compensated for by enhanced chances of reproduction. Finally, dispersalincreases after the high mortalit...